1. Field of the Invention
The present invention relates to a headlamp for use with vehicles such as automobiles, motorcycles and motorized bicycles.
2. Description of the Prior Art
In general, the construction as shown in FIGS. 1 and 2 is known as a headlamp for vehicles. The known headlamp has a reflector 1 having a parabolic surface and a lens 2 made of glass at the front of the reflector. A light source 3 is positioned in the vicinity of the focal point of the reflector 1 to direct the light emitted from the light source 3 to the lens 2 through reflection by the reflector 1.
In the conventional headlamp thus constructed, if the light source 3 used for, for example as the high beam or passing light, is energized, the reflected light a (see FIG. 1) from the reflector 1 is concentrated at one portion on the lens 2 as shown by the region A in FIG. 2, thereby resulting in the region A of the lens 2 being at a most high temperature. This condition is shown in FIG. 2, showing the reflected light being highly concentrated at the upper portion of the reflector 1 and lens 2. As shown by the temperature distribution curve in FIG. 3, the portion A of the upper and central portion of the lens 2 reaches a high temperature such as 142.degree. C. Therefore, there has been the problem that a plastic lens having a good molding performance and light weight can not be adopted for the lens 2 of the headlamp, since such plastic materials would not properly withstand such high concentrated heat.